Experimental investigation on coal and char combustion in O₂/CO₂ mixture

Thermogravimetric analyzer (TGA) was employed to evaluate the combustion behaviors of Xuzhou bituminous coal and its char in different atmospheres, and the effects of O₂ concentration, CO₂ concentration and particle size on the combustion characteristics were analyzed. Results show that the atmosphere does not affect the beginning time of devolatilization, but significantly affect the combustion rate and the burnout time. Higher concentration of CO₂ can increase the burnout time obviously. However, the atmosphere does not influence the combustion kinetics mechanism. Increasing the O₂ concentration, decreasing the CO₂ concentration and reducing the sample particle size are beneficial to the improvement of the combustion characteristic, while the improvement degree for coal is more obvious than that for char. SEM analysis indicates that the ash surface after O₂/CO₂ combustion is looser and more porous than that after air combustion.